Book/Report

FZJ-2019-01439

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Untersuchungen an dünnen Schichten mit Photoelektronenbeugung und Rastertunnelmikroskopie

Scheuch, V. (Corresponding author)FZJ*

1996
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich

Please use a persistent id in citations: http://hdl.handle.net/2128/21629

Report No.: Juel-3228

Abstract: The application of x-ray photoelectron eliffraction (XPD) anel scanning tunneling microscopy (STM) to epitaxial thin film systems reveals interesting information ab out their growth behaviour anel structure. Photoelectron eliffraction in its two implementations of angular scanning (azimuthal and polar) showed structural transformations in two different heteroepitaxial systems. The growth of Co/Cu(111) is connected with the transition of fcc to hcp Co within the first few atomic layers which is evident by the change from threefold to sixfold symmetry of the azimuthal XPD patterns. The growth mode has been determined to be non-layer-by-layer due to distinct forward scattering features in the submonolayer range. The use of 1 ML preadsorbed Sb results in a flatteneel growth mode which is accompanied by Sb surface segregation (surfactant effect). Moreover, Sb delays the completion of the fcc $\rightarrow$ hcp transition to beyond 10 ML. The transition of the bcc lattice towards the NaCl structure has been found by investigating surface segregation phases on a Fe-15%Cr(100) single crystal with polar XPD. Diluted N and C co-segregate with Cr by heating the sample, forming ordered CrN anel CrC phases, respectively. While the interlayer spacing of a thin CrN layer is expanded by 15% with respect to the substrate, the structure is NaCl like for a thicker layer corresponding to the bulk CrN lattice. Even a threedimensional CrC phase which is not known in the bulk could be stabilized in the NaCl structure. This can be easily determined by the position of forward scattering maxima. An STM study of the nucleation of CoSi$_{2}$ on Si(100) as an example for thin film silicide growth showed the existence of both two- and threedimensional islands of different structure. The 3d-islands have different epitaxial orientations and their growth is connected with a substantial mass transport from the substrate into the islands. Voltage-dependent STM revealed a mixed ($\sqrt{2}$ x $\sqrt{2}$) R45° structure on top of some islands, which seems to consist of both Co and Si atoms being irregularly distributed. Thicker layers have been grown by co-deposition of Co anel Si resulting in a rough surface which is formed by large CoSi$_{2}$ precipitates. These films can be smoothed by the use of 1 ML preadsorbedAs which results in a reduced roughness and an increased island density, thus As acts as a surfactant.

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Contributing Institute(s):

1. Publikationen vor 2000 (PRE-2000)

Research Program(s):

1. 899 - ohne Topic (POF3-899) (POF3-899)

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